1. Field of the Invention
The present invention relates to a solid-state image pickup apparatus, and in particular, to a solid-state image pickup apparatus of the charge transfer type which delivers video signals according to the interlaced scanning whereby each frame includes two fields.
2. Description of the Related Art
In a solid-state image pickup device of so-called interline transfer type, for example, photocarriers generated in photosensitive cells arranged in a matrix array on a light receiving surface thereof are first moved to vertical transfer paths constructed in a charge coupled device (CCD) structure so as to be transferred in a vertical direction; next, the photocarriers are fed to a horizontal transfer path also in the CCD structure to be transferred in a horizontal direction, thereby delivering these photocarriers in the form of video signals.
In the standard television systems such as the NTSC, for example, raster scanning video signals are configured according to the two-field for one-frame interlaced scanning process. When using the solid-state image pickup device of the interline transfer type in the ordinary television system, so-called frame and field signal store systems are applicable.
For example, if the frame signal store system is adopted in the interline transfer process, photocarriers generated by the light incident on the photosensitive cells during a 1/30-second frame period are delivered to the vertical transfer paths. In a case of the field store system, such photocarriers generated in the cells during a 1/60-second field period are moved to the vertical transfer paths. When using the interlaced scanning process together with the frame signal store system, video signals of an odd-numbered horizontal line and those of an even-numbered horizontal line are alternately read out for every consecutive two fields. That is, for the video signals of this system, different portions of an image are contained in fields A and B, respectively; and hence a field flicker noise is caused to occur. This adverse effect becomes considerable especially when reproducing a still picture from video signals of an image moving at a high speed.
In the field signal store system, on the other hand, video signals of an odd-numbered line and those of an even-numbered line are read out after being alternately subjected to addition for each field. The addition is conducted in such a fashion that video signals of lines or rows n and n+1 are added for a field and those of rows n-1 and n are added for the other field. Consequently, image information is averaged between the adjacent horizontal rows, which leads to a disadvantage that the vertical resolution of an image is deteriorated.